Relationship between muscle T^sub 2^^sup ^ relaxation properties and metabolic state: a combined localized ^sup 31^P-spectroscopy and ^sup 1^H-imaging study

A multi-volume ^sup 31^P-magnetic resonance spectroscopy localization procedure was implemented to compare directly muscle metabolism and proton T^sub 2^ ^sup *^ relaxation properties in the human plantar flexor muscles during exercise. Localized ^sup 31^P-spectra were collected simultaneously from the medial gastrocnemius, lateral gastrocnemius and soleus muscles during exercise using β ^sub 1^-insensitive Hadamard Spectroscopic Imaging (HSI). ^sup 1^H T^sub 2^ ^sup *^-weighted gradient-echo images were acquired at rest and immediately following high-intensity plantar flexion exercise. T^sub 2^ ^sup *^ mapping of the individual calf muscles showed that plantar flexion with the knee extended produces significant increases (P